An 'ab initio' investigation of the electronic structure of ion-pair enolates NH2COCH2CuPH3, PH2COCH2CuPH3, C6H5COCH2CuPH3, C6H5SOCH2CuPH3: the influence of the heteroatom. Part III

The electronic structure and the geometry of the phosphinecopperacetamide, the phosphinecopperactylphosphine, the phosphinecopper-acetophenone and the phosphinecoppermethylphenylsulfoxide have been investigated through ab ini tio calculations. The different coordination modes, eta(1)-O, eta(3) and et a(1)-C of the CuPH3+ cation have been analyzed. The eta(1)-C coordination o f the copper towards the enolate anion is preferred for the acetamide, whil e the eta(3) coordination is the lowest in energy for the methylphenylsulfo xide. For the acetylphosphine and the acetophenone enolate anions the eta(1 )-O and eta(1)-C coordinations are almost isoenergetic, while the eta(3) co ordination is higher in energy. A comparison between CuPH3+ and TiF3+ inter acting with the same enolate anions, shows that a soft metal like copper st abilizes the eta(1)-C coordination, while a hard metal like titanium prefer s the interaction with the other nucleophilic center, i.e. the oxygen. (C) 1999 Elsevier Science B.V. All rights reserved.